During the various transformation phases occurring in the elaboration of a strap-like product, and especially a metal sheet, it is often contemplated to wind the strap into a reel, for instance to maneuver, store or move it more easily.
To perform some kind of processing on the strap, such as rolling or surface coating, cleaning, etc., it must be unwound and transferred using a series of backing and driving rolls. During this process, the strap winds around the various rolls on a contact sector, and metal particles or various contaminants may get stuck on the surfaces of these rolls.
These particles have a tendency to build up and get encrusted on the rolls, leaving marks on the rolls as well as the strap. Damage caused by such particles have serious consequences. For instance, in the metal industry, during rolling, many particles from the sheet unavoidably get stuck on the working rolls or the backing rolls, causing deterioration of the surfaces of the rolls and periodic marking of the strap. Reels may be rejected because of surface imperfections. It is then necessary to change the rolls to have them remachined much more often than required under normal wear. This is very costly, especially when rolls coated with a rubber layer or any other metal or organic coating are used.
It has therefore been attempted to clean the rolls during operation in order to remove the particles or other contaminants before contact with the strap and avoid their incrustation.
At the outset, this cleaning was performed manually but, taking the space requirements of the installation and the passage speed of the strap into account, this operation was relatively dangerous and, in any case, did not produce a satisfactory result.
Thus it was suggested to wipe, clean ore polish the rolls without any manual intervention, using devices enabling the roller to be contacted directly by a cleaning tool such as a rotary brush or a scraping device.
JP 3-149.165, for instance, shows such an apparatus, designed to perform the polishing of one of several rolls associated with parallel axes. This apparatus comprises two rotary grinding wheels mounted on a first movable carriage, parallel to the axes of the rolls, on a second carriage itself slidingly mounted on two straight guiding devices apart from one another, and defining a sliding plane of the grinding wheels parallel to the axes of the rolls and adapted to be directed toward either axis thereof by pivoting of the guiding devices around an axis which is adjustable in height. It thus becomes impossible to direct the sliding plane radially towards the axis of the roll to be polished by adjusting the height of the axis and the orientation of the guiding means, then to locate the grinding wheels in contact with the roll by causing the second carriage to slide.
It could be contemplated to replace the grinding wheels with rotary brushes, but such an apparatus is relatively encumbering and not readily applicable to the mills in which the space requirements are often quite restricted, between the rolled strap and the rolls, to place the cleaning apparatus. The cleaning apparatus must allow introduction into this restricted area until it contacts the rolls to be cleaned and, periodically placed in a position enabling maintenance or replacement of the cleaning tool, preferably without stopping the passage of the rolled strap.
DE-A-1.943.847, which applies to the maintenance of the working rolls of a Quarto-type mill, shows an apparatus comprising rotary brushes carried, at their ends, by two supports which can be moved parallel to themselves in order to contact the working roll to be cleaned or to move apart to a remote position. However, even in this position, the brushes are still close enough to cult to disassemble them.
Besides, in the case of sheet metal rolling mill installations, it is sometimes preferred to use, for cleaning the rolls, a wiping tool in the form of a stripping ruler parallel to the roll axis and made of a stone or a resin associated with an abrasive, which can be applied to the roll by means bearing on a supporting device, for instance pneumatic or hydraulic cylinders.
U.S. Pat. No. 4,841,675 shows an apparatus in which the cleaning tool is made of several stones located one behind another and carried by a stem parallel to the longitudinal axis of the roll. Every stone is applied elastically on the roll by an arm attached to the stem via an elastic bush which allows the stone to suit the profile of the roll. The supporting stem can be moved alternately in an axial direction in order to homogenize the cleaning operation. The assembly is placed on a chassis attached on the cage at the level of the roll to be cleaned and that can be moved horizontally in order to apply the cleaning tools on the roll or move them apart to enable dismantling.
Such a device is relatively encumbering and therefore, in the case of U.S. Pat. No. 4,841,675, it is applied to the cleaning of the backing rolls of the mill. Conversely, it could hardly be used for cleaning the working rolls since the cleaning tools must move within a very narrow area, restricted on one side by the backing roll and, on the other, by the passing strap. Besides, the mills are often fitted with somewhat encumbering ancillary devices, located close to the strap. Especially the skin-pass type mills are associated with antipleating rolls or others, themselves mounted on adjustment devices diminishing further the area available to access the working rolls.
Besides, dismantling all the stones takes a long time and requires extended shut-down of the line.
Moreover, the stones are attached independently on the supporting stem, each via an arm linked to the stem by an elastic ring, and it is difficult enough to adjust the backing pressure of the stones uniformly over the entire length of the roll.
Finally, the system possesses a larger cantilever which reduces the quality of the cleaning and may cause vibrations, especially if it is necessary to reduce the size of the supporting chassis in order to limit the encumbrance.
Therefore, in the case of rolling mills, it is often preferable to eliminate the wiping tool and to perform the cleaning by simple detergent projections, but these are powerless against incrustation of solid particles and require working in a humid environment.